Messages in this thread | | | Date | Mon, 18 Apr 2011 08:51:50 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/4] x86, gart: Don't enforce GART aperture lower-bound by alignment |
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On 04/18/2011 07:56 AM, Roedel, Joerg wrote: > On Mon, Apr 18, 2011 at 10:45:19AM -0400, H. Peter Anvin wrote: >> On 04/18/2011 06:45 AM, Joerg Roedel wrote: >>> This patch changes the allocation of the GART aperture to >>> enforce only natural alignment instead of aligning it on >>> 512MB. This big alignment was used to force the GART >>> aperture to be over 512MB. This is enforced by using 512MB >>> as the lower-bound address in the allocation range. >>> >>> Cc: Yinghai Lu <yinghai@kernel.org> >>> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com> >> >> Better implementation of the existing bounds, yes, but I think the >> algorithm is still wrong. Specifically, 512 MiB seems to have been the >> maximum address of the kernel at some point, but that is historic at >> this point, at least on 64 bits. > > I am fine with a smaller lower-bound, but I am not sure what a better > choice is. The comment about kexec seems to be valid. It shouldn't matter > for kdump because in this case the memory is allocated independently and > the kdump kernel will only use this part, but for other kexec uses it is > a bit harder. Probably any number we choose as a lower bound is an > arbitrary choice at some point. But I am open for > suggestions/corrections to this. >
The right thing to do for in-place kexec it to turn it off, not rely on any specific magic addresses. We have had this problem with a number of drivers in the context of kexec.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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